On paper, the plot doesn't really bring anything new to the table. It's the same May-December dynamic you've probably read elsewhere.
The execution, though, is better than expected in terms of average shoujo manga. The heroine, refreshingly, doesn't come from the "crybaby but works hard so she's lovable" block. One chapter briefly touches on her spotty past, but it makes a great jump-off point to the story's theme of second chances and redemption. She is also surprisingly pragmatic, despite being a teenage girl in love.
The male protagonist doesn't come off as icky to me. His transition from mentor to friend to "something more, maybe" felt natural
and unforced. His previous relationship hangups didn't feel like a big deal enough to be treated as a conflict, but otherwise, I liked how he was depicted.
The flower motif tied very well with the lessons the manga wanted to impart. Plus, I learned a lot of nifty things about being a florist! Good research and integration into the plot.
After finishing the manga, I felt quite fulfilled. The ending was not solely about how her love story turned out, but also how she and the other people around her changed over time.